Got detonation issues w/ 331, could it be my 30's near their max???

[houstonstangguy]

after it was dyno'd and tuned in december i didnt notice any issues right away, but after some time I did but only up in the higher rpm range, and only when I hammer it. i am running 3924 plugs, not sure the gap, a very good tuner here in houston did it. fuel psi is up at 46, timing was 15*. I backed the timing to 14, then 13, then 12, then 11 where it sits now. I tried replacing the fuel filter, and it still did it.

someone in my club told me that based on my rwhp numbers my 30's could be pushing up near their max and that could be why when I hammer it up high is where I hear the detonation.

any ideas???
have to go to my morning class but I will check any replies when I get home.

thanks, much appreciated,

Joe

 

[SmockDoiley]

Well 19's can handle like 300 at the flywheel, so theres no reason why your 30's couldnt handle 410 at the fly. Before you do anything, you should some how see what your A/F ratio is across the board. This will answer your question before you go replacing expensive stuff.

 

[86Cobra]

30s should be fine at that power level. What's your compression ratio?

 

[autoXr1]

I'm running 30# FMS injectors on my combo...see sig. Anyhow, it would seem that if it were a fuel delivery problem, it would have showed up on the first dyno tune. Your problem appears to have developed over time and suggests a different situation. If you have unburnt fuel leaving carbon deposits in your combustion chambers, it raises your compression ratio over time, leading to an increasing tendency for predetonation. So, what do you do...raise the octane level of the fuel, back off on the timing...this in turn, only serves to aggrevate the problem. Sure, it helps in the short term, but as you have found out, the problem resurfaces later on.

My suggestion is to run some fuel system cleaner and some engine oil system cleaner through the engine with your next fill-up and oil change. Talk to your tuner in regards to the possibility that your engine may actually be tuned a little RICH,...or...that you may have a weak ignition system that isn't burning the fuel as it should. A wide-band O2 sensor should tell the story. Perhaps it's time for another visit to your shop.

My .02

 

[N8Miller]

i agree with 86 cobra, i dont think its the 30s, they should work good.

 

[houstonstangguy]

thanks for the feedback guys. other than reusing my cobra intake and throttle body, the rest of the setup was thought out pretty well and I figured that the 30's had plenty of room in them for the setup and the nos kit that i ended up selling. i just thought i would ask your thoughts on the injectors even though i never really doubted they would be ok.

let me throw this out. since i always had iron heads on all of my other applications, it didnt really occur to me that when i threw in autolite 24's instead of 3924's they were too short in there and would cause carbon buildup. as soon as i took it in to the tuner he drove it and asked which plugs i was running and when i told him he said that was a big part of my problem (ok i had a brain fart, dont laugh).

i want to say that he sprayed something in there to get rid of the carbon but i could be mistaken. is it possible that after all this time there is still carbon built up in there?

let me know,
Joe